Method of joining sintered parts of different sizes and shapes

ABSTRACT

A method of joining a plurality of parts to form a unitary body includes providing at least two sintered parts. Each of the parts is formed of a hard metal composition of material. The sintered parts are assembled into the shape of a unitary body. Each of the sintered parts has a joining surface and when each joining surface is brought into contact the surfaces form a bonding interface therebetween. The assembled sintered parts are subjected to a temperature sufficient to fuse the sintered parts together at the bonding interface to form the unitary body. A wear resistant tool includes a plurality of sintered parts, each of the sintered parts is formed of a hard metal composition of material, wherein the plurality of sintered parts can be assembled into a unitary body, wherein the assembled parts are fused together at a respective bonding interface to form the unitary body.

TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY

The present disclosure relates to a method of joining different sized and/or shaped parts or members to form a unitary body, and more particularly, to a method for joining sintered parts of different sizes and/or shapes to form a unitary tool or wear part.

SUMMARY

In one aspect there is provided a method of joining a plurality of parts to form a unitary body. At least two sintered parts are provided. Each of the parts is formed of a hard metal composition of material. The at least two sintered parts are assembled into the shape of a unitary body. Each of the at least two parts has a joining surface and when each joining surface is brought into contact the surfaces form a bonding interface therebetween. The assembled parts are subjected to a vacuum or gas atmosphere, without the application of external pressure, and to a temperature sufficient to fuse the at least two sintered parts together at the bonding interface to form the unitary body.

In another aspect a wear resistant tool includes a plurality of sintered parts. Each of the parts is formed of a hard metal composition of material, wherein the plurality of sintered parts can be assembled into a shape of a unitary body. A joining surface is disposed on each of the plurality of sintered parts, wherein when the parts are assembled each joining surface is brought into contact to form a bonding interface therebetween, such that when the assembled parts are subject to a vacuum or gas atmosphere, without the application of external pressure, and to a temperature sufficient to fuse the plurality of parts, the plurality of parts are joined together at a respective bonding interface to form the unitary body.

In still another aspect, a method of joining a plurality of sintered materials to form a unitary wear resistant tool includes the step of providing a plurality of sintered parts, each of the sintered parts being formed of a hard metal composition of material. The plurality of sintered parts is assembled into a shape of a unitary body. Each of the plurality of sintered parts has at least one joining surface and when each joining surface is brought into contact the joined surfaces form a bonding interface therebetween. The assembled parts are subject to a vacuum or gas atmosphere, without the application of external pressure, and to a temperature sufficient to fuse the plurality of parts together at the bonding interface to form the unitary wear resistant tool.

These and other objects, features, aspects, and advantages of the present disclosure will become more apparent from the following detailed description of the preferred embodiment relative to the accompanied drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram illustrating the steps of the present method.

FIG. 2 is a perspective view of a body made according to the process of FIG. 1.

FIG. 3 is a perspective view of a plurality of members disposed in a fixture for joining according to the present method.

FIGS. 4( a)-4(c) are respective cross-sections taken along the indicated lines of FIG. 3.

FIG. 5 is a cross-sectional view of another body formed according to the present method.

FIG. 6 is a cross-sectional view of yet another body made according to the present method.

FIG. 7 is a cross-sectional view of still another body made according to the present method.

DETAILED DESCRIPTION

High wear resistant materials, such as cemented carbide, are popular for rock and metal drilling tools and for wear parts. Bodies of these materials are usually made by powder metallurgical methods, namely, pressing and sintering.

There are numerous methods for joining multi-member cemented carbide bodies. A multi-member cemented carbide body can be independently formed of distinct green bodies. Sometimes, the independently formed green bodies are also independently sintered and, sometimes after grinding, assembled, for example, by soldering, brazing, direct pressing or shrink fitting to form a multiple-region cemented carbide body. Hence, the desired form of the sintered body is usually obtained before sintering after which the partial bodies are sintered together to form a body with a desired, often complex geometry, because machining of the sintered body is expensive.

For example, standard methods of producing multi-sized tools involve producing parts having the maximum size and then removing material before sintering, after sintering or both. This results in a significant amount of the cemented carbide being lost.

Alternatively, independently formed bodies are assembled and then sintered. However, the different combinations of the same ingredients that comprise the independently formed bodies respond to sintering differently. Each combination of ingredients responds uniquely to a sintering temperature, time, atmosphere or any combination of the proceeding and thus shrinks uniquely.

Moreover, there is the disadvantage due to the large amounts of liquid phase migrating significant distances into each of the bodies. This sometimes results in severe compositional changes.

It is known to form complex shaped articles comprised of dissimilar materials, wherein the interface between the materials may be very narrow. See U.S. Pat. No. 6,315,945 wherein pluralities of separate bodies are arranged such that each separate body is in contact with at least one other separate body to form an aggregate body. The aggregate body is then consolidated at a temperature, superatmospheric pressure, time at temperature and time at the superatmospheric pressure sufficient to form a consolidated shaped article. The consolidated shaped article has a shape defined by each of the separate bodies used to make the article. However, the use of superatmospheric pressure is time consuming and expensive.

U.S. Pat. No. 6,908,688 also discloses the use of superatmospheric to form a hard metal tool having different joined bodies. In this and in the other known methods significant migration of the constituents across the boundary of the parts occurs. This can lead to precipitation of embrittling phases and long gradient zones of intermediate properties, causing, in severe cases, large scale density changes and consequent distortion of the parts.

Thus, there is a need for a method of joining or fusing, pre-sintered members to form a tool of complex geometry without the need for pressure, grain growth at the boundaries or wasting of expensive material.

Referring to FIGS. 1 and 2, a method of bonding or joining at least a pair of parts is described. In a first step 12, a plurality of parts, sections or members 32, 34 and 36 are provided. The parts can be of the same size or shape or different sizes or shapes and/or of the same or different material. It should also be appreciated that numerous parts can be joined according to the present disclosure, which should not be limited to a particular number of parts used to form a single, unitary body 30. A unitary body is defined as a singular body connected parts. For example, body 30 can be a step drill having different diameter parts.

Parts 32, 34 and 36 can be made from hard metal compositions of compacts of liquid phase sintered materials which include low melting phase components and high melting phase components A hard metal composition is a composite material having a hard phase composed of tungsten one or more carbides, nitrides or carbonitrides of tungsten, titanium, chromium, vanadium, tantalum, niobium bonded by a metallic phase binder typically cobalt, nickel, iron or combinations thereof in varying proportions, such as a cemented carbide or cermet. A cemented carbide has a hard phase composed of tungsten carbide and of one or more carbides, nitrides or carbonitrides of titanium, chromium, vanadium, tantalum, niobium bonded by a metallic phase binder typically cobalt, nickel, iron or combinations thereof in varying proportions. A cermet has a hard phase composed of one or more carbides, nitrides or carbonitrides of titanium, chromium, vanadium, tantalum, niobium bonded by a metallic phase typically cobalt, nickel, iron or combinations thereof in varying proportions.

Cemented carbides and cermet exist in different grades. Grade refers herein to a cemented carbide or cermet, in one of several proportions and with a certain grain size. A high quality grade is a material with a quantifiably greater performance and reliability in a given application.

For example, the parts can be cemented carbide of the same composition, or two or more different compositions and being different with respect to grade and/or grain size that are fused together, as will be described further herein. Cemented carbide

Each part has been sintered for obtaining substantially the full density and hardness thereof. See step 14. Each part has a joining surface 28. In step 16 the parts are ground or machined at the mating/joining surfaces to provide a sufficiently smooth finish between the parts. The parts can also be cleaned, for example, in a hydrogen cleaning process, to provide a clean interface at the joining surfaces. Thereafter, the individual, parts are assembled into the desired tool shape in step 18.

Step 20 involves bringing the parts into contact in an assembled relationship with a first bonding or joining surface 28 between two of the parts in mating engagement with a second bonding or joining surface between the other of the members to each define a bonding or boundary zone 26. Thereafter, the step of heating the parts in the assembled relationship is employed to fuse the members together.

In step 20, the parts are fused at a temperature low enough so that no grain growth occurs. For example, of about 1340° C. to about 1360° C. for about 10 to about 30 minutes, and more preferable about 1350° C. for about 15 minutes. In other words, the parts are fused at a temperature lower than or intermediate to the melting point of the hard metal composition having the lowest original sintering temperature of the parts. This lower temperature and shorter time enables the fusing to proceed by short range diffusion of the binder metals across the interface and no grain size changes are induced in the microstructures.

Referring to FIG. 3, in one example, the assembled body 30 is placed on a plate 40 that is placed in a standard sintering furnace. A vacuum or gas atmosphere is used during the sintering process to control the environment. The body is then brought from room temperature to the fusing temperature of about 1350° C. or higher depending on the composition, at about 450° C. per hour with about a 15 minute dwell time at the top temperature. This fusing temperature and heat cycle is lower than the original sintering temperatures and heating cycles of the part(s) of the body having the lowest melting temperature.

This step takes the already dense and hard piece of carbide and puts it back into the sintering furnace. But, instead of getting shrinkage and a more density, as in the first sintering operation, the part remains essentially the same in physical properties. The minimal amount of liquid phase occurs, but still bonding is enabled to take place.

Referring again to FIGS. 2 and 3, the present method enables joining of sintered rods having different diameters to form a unitary tool or wear part. According to one aspect of the method a plurality of sintered rods 32, 34, and 36, each having a different diameter, are provided. The rods can be assembled to form a unitary body.

Although a multi-diameter body 30 is described in this example, it should be appreciated that, and as shown in the following examples, a body made of different material, sized or shaped members can be made according to the present method. Accordingly, the sizing and/or shaping of the members are a function of the particular unitary body or tool desired and the particular physical and/or dimensional characteristics are therefor according to satisfactorily meet an intended use.

As shown in FIG. 3, body 30 is positioned in a fixture 40. Referring to FIGS. 4( a)-(c), each member is positioned on fixture 40 such that the longitudinal axis of each member is in the same plane X. FIG. 4( a) is a cross-section of fixture 46 taken along line I-I of FIG. 3. FIG. 4( b) is a cross-sectional view taken along line II-II. FIG. 4( c) is a cross-sectional view taken along line III-III. As shown, member 36 is located in a grooved portion of a first block 42 that is fixed directly to a plate 46 of the fixture. In order to align the axis of rod 34 with that of rod 36, a platform 44 is provided. Likewise, block 42 supporting rod 32 is positioned on two platforms 44. Plate 46 is inclined and blocks 42 are positioned such that the respective rods are pressed together at interfaces 28, 38 to enables bonding zones 26 during sintering.

As set forth above, like the provision of particular members are dependent upon the end part or tool desired, the arrangement of the fixture 40 is too dependent upon the particular members and desired unitary body. Accordingly, the present method is not limited to a particular fixture design.

The method can be additionally illustrated in connection with the following, which should be understood to be illustrative and not limiting.

Different grade materials can be joined to optimize local properties of, for example, the tool or wear part. Thus, for example, wear resistance, toughness, brazability, friction coefficient and/or cubic boron nitride (cBN) content of a material can be chosen depending on the location of the material in the tool or wear parts. Moreover, a cobalt or grain-size mismatch can also be chosen to induce binder metal fusing and consequent density changes. This can induce compressive stresses at the tool or part surfaces to provide a toughening effect. Also, multilayers having large cobalt content or grain size mismatch can be incorporated for crack deflection.

The following are just some examples of providing dissimilar grade/shaped materials formed according to the present methodology.

Referring to FIG. 5, the present method can be used to produce a drill or tool having a plurality of materials as different portions of the tool. Although three different materials are described with reference to this aspect, it should be appreciated that a number of different materials can be joined. A drill 50 can have different types of hard metal compositions fused together according to the present method. As shown, a premium or high quality grade material 52 can be located at a point 54. Another higher grade material 56 can be provided at a cutting edge 58 of the tool. For example, materials 52 and 56 can be a high grade material such as Sandvik Hard Materials H12N and 6UF (Sandviken, SE) doped with cBN for the high wear or cutting surfaces.

A third material 60 having a different grade can be used for a shank 62 of the drill. For example, material 60 can be powders reclaimed zinc (PRZ) carbide that has been recycled/reclaimed using molten zinc. Material 60 can be any lower cost material and the present aspect should not be limited to any particular method of recycling or sourcing but only such that would reduce the cost of the material. By using PRZ or some proportion of a recycled material as a base material with a premium work face the sustainability via a high recycling content and reduced cost is obtained.

Referring to FIGS. 6 and 7, the present method can be used to form a twist to straight long drill (FIG. 6) and a variable twist drill (FIG. 7). As shown in FIG. 6, a long drill 80 for deep drilling can include a straight hole main section 76 fused to a helical end 78. Section 76 can be flute free, i.e., without a flute. Section 78 includes a flute 79. Such an arrangement minimizes the swarf path and/or very aggressive cutting without clogging from swarf. It should be appreciated that straight section 76 and helical end 78 can be formed of different materials. Alternatively, an extruded section with flutes can be fused to the shank.

As shown in FIG. 7, the helix angle of a drill 90 can be varied by fusing a number of sections 84, 86 and 88 together, where each section is a preformed fluted part having a different helix angle. It should be appreciated that any number of sections can be fused together. Moreover, the sections can be of the same or different materials. Carbide with different properties and/or with high proportions of recycled material could be used for some of the sections and fused thereto. As described above, a drill point of the drill can be made of a different material 82. Material having independently optimized properties can be used for different parts of a composite tool requiring different properties or having different demands placed thereon, for example, lower quality composition, such as a low quality carbide, and a higher quality material. This aspect allows for different helix angles to be joined. However, parallel webs would be necessary. Further, different flutes could be fused to sections according to the present method.

The disclosed method can be used to build complex shapes from a stock of different parts allowing for under cuts, side holes, voids, profile changes etc., but avoiding MAP/PIM or machining.

Most importantly, any of the above features can be combined in a single tool or part. For example, different parts can be carefully selected and joined together to suit particular applications where wear, chemical resistance, etc. is required.

The present methodology offers many advantages, included but not limited to, significant cost savings and environmentally friendly production. Key advantages also include formation of complex shapes not possible by conventional processing or machining. Also material combinations not possible by current methods can be achieved.

Although the present disclosure has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred therefore, that the present disclosure be limited not by the specifics disclosed herein, but only by the appended claims. 

What is claimed is:
 1. A method of joining a plurality of parts to form a unitary body comprising the steps of: providing at least two sintered parts, each of the parts being formed of a hard metal composition of material; assembling the at least two sintered parts into a shape of a unitary body, wherein each of the at least two parts has a joining surface and when each joining surface is brought into contact the joined surfaces form a bonding interface therebetween; and subjecting the assembled parts to a vacuum or gas atmosphere, without the application of external pressure, and to a temperature sufficient to fuse the at least two sintered parts together at the bonding interface to form the unitary body.
 2. The method of claim 1, wherein the hard metal composition of material is cemented carbide.
 3. The method of claim 2, wherein the cemented carbide has a hard phase of tungsten carbide and of one or more carbides, nitrides or carbonitrides selected from the group of titanium, chromium, vanadium, tantalum, niobium bonded by a metal phase selected from the group of cobalt, nickel, iron and combinations thereof.
 4. The method of claim 2, wherein each of the at least two sintered parts is made of the same cemented carbide.
 5. The method of claim 2, wherein each of the at least two sintered parts is made of a different cemented carbide.
 6. The method of claim 1, wherein the hard metal composition of material is a cermet.
 7. The method of claim 6, wherein the cermet has a hard phase selected from the group of one or more carbides, nitrides or carbonitrides of titanium, chromium, vanadium, tantalum, niobium bonded by a metallic phase selected from the group of cobalt, nickel, iron and combinations thereof.
 8. The method of claim 2, wherein the assembled parts are heated to a temperature lower than a melting point of the lower sintering temperature of each of the at least two sintered parts to fuse the parts at the bonding interface.
 9. The method of claim 8, wherein the assembled at least two sintered parts are heated to a temperature of about 1340° C. to about 1360° C.
 10. The method of claim 9, wherein the assembled at least two sintered parts are heated for a time period of about 10 to about 30 minutes.
 11. The method of claim 8, wherein the assembled at least two sintered parts are heated to a temperature of about 1350° C. for about 15 minutes.
 12. The method of claim 1, wherein each of the at least two sintered parts has a different shape.
 13. The method of claim 1, wherein the unitary body is a wear resistant tool.
 14. The method of claim 1, wherein the unitary body is a tool blank.
 15. The method of claim 1, wherein the unitary body is a wear part.
 16. The method of claim 1, wherein each of the at least two sintered parts has a different size.
 17. The method of claim 1, wherein a plurality of sintered parts are provided.
 18. The method of claim 13, wherein the tool is a drill and wherein a first sintered part forming a shank of the drill made of a first grade of hard metal composition of material, a second sintered part forming a cutting edge of the drill made of a second grade of hard metal composition of material, and a third sintered part forming the point of the drill made of a third grade of hard metal composition are provided.
 19. The method of claim 18, wherein the third sintered part is of a higher quality grade than a grade of the first and second sintered parts.
 20. The method of claim 17, wherein each of the plurality of sintered parts is a different sized sintered rod, each of the plurality of sintered rods having a different size diameter.
 21. The method of claim 1, wherein the tool is a drill and a plurality of sintered parts are provided, each of the sintered parts forming a section of the drill.
 22. The method of claim 21, wherein a first section is flute free and at least one other section is fused to the first section, the at least one other section being fluted and each of the sections being formed of a different hard metal composition of material.
 23. The method of claim 21, wherein at least two sections of the drill are fluted and wherein each of the fluted sections has a different helix angle.
 24. A wear resistant tool comprising: a plurality of sintered parts, each of the sintered parts being formed of a hard metal composition of material, wherein the plurality of sintered parts can be assembled into a shape of a unitary body; and a joining surface disposed on each of the plurality of sintered parts, wherein when the parts are assembled each joining surface is brought into contact to form a bonding interface therebetween, such that when the assembled parts are subject to a vacuum or gas atmosphere, without the application of external pressure, and to a temperature sufficient to fuse the plurality of parts, the plurality of parts are joined together at a respective bonding interface to form the unitary body.
 25. The wear resistant tool of claim 24, wherein each of the plurality of sintered parts has a different size.
 26. The wear resistant tool of claim 24, wherein each of the plurality of sintered parts has a different shape.
 27. The wear resistant tool of claim 24, wherein the hard metal composition of material is cemented carbide.
 28. The wear resistant tool of claim 27, wherein the cemented carbide has a hard phase of tungsten carbide and of one or more carbides, nitrides or carbonitrides selected from the group of titanium, chromium, vanadium, tantalum, niobium bonded by a metal phase selected from the group of cobalt, nickel, iron and combinations thereof.
 29. The wear resistant tool of claim 27, wherein each of the plurality of sintered parts is made of the same cemented carbide.
 30. The wear resistant tool of claim 27, wherein each of the plurality of sintered parts is made of different cemented carbide.
 31. The wear resistant tool of claim 24, wherein the hard metal composition of material is a cermet.
 32. The wear resistant tool of claim 31, wherein the cermet has a hard phase selected from the group of one or more carbides, nitrides or carbonitrides of titanium, chromium, vanadium, tantalum, niobium bonded by a metallic phase selected from the group of cobalt, nickel, iron and combinations thereof.
 33. The wear resistant tool of claim 24, wherein the assembled parts are heated to a temperature lower than a melting point of the lower sintering temperature of each of the plurality of sintered parts to fuse the parts at the bonding interface.
 34. The wear resistant tool of claim 24, wherein each of the plurality of sintered parts is a different size.
 35. The wear resistant tool of claim 24, wherein the tool is a drill and wherein a first sintered part of a first grade of hard metal composition of material forms a shank of the drill, a second sintered part of a second grade of hard metal composition of material forms a cutting edge of the drill, and a third sintered part made of a third grade of hard metal composition forms a point of the drill.
 36. The wear resistant tool of claim 35, wherein the third sintered part is of a higher quality grade than a grade of the first and second sintered parts.
 37. The wear resistant tool of claim 24, wherein each of the plurality of parts is a different sized sintered rod, each of the plurality of rods having a different sized diameter.
 38. The wear resistant tool of claim 24, wherein the tool is a drill and each of the plurality of sintered parts form a section of the drill.
 39. The wear resistant tool of claim 38, wherein a first section is flute free and at least one other section is fused to the first section, the at least one other section being fluted and each of the sections being formed of a different hard metal composition of material.
 40. The wear resistant tool of claim 39, wherein at least two sections of the drill are fluted and wherein each of the fluted sections has a different helix angle. 